San Leon, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 18.3 °C (low) to 24.1 °C (high). Annual precipitation averages 1473.2 Millimeters. San Leon is located in USDA Plant Hardiness Zone 10a.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.8 °C | 15.9 °C | 118.11 mm |
| February | 10.8 °C | 17.4 °C | 80.26 mm |
| March | 14.3 °C | 20.3 °C | 85.6 mm |
| April | 17.9 °C | 23.3 °C | 107.7 mm |
| May | 22.1 °C | 26.8 °C | 126.49 mm |
| June | 25.2 °C | 29.6 °C | 149.35 mm |
| July | 26.1 °C | 30.9 °C | 116.59 mm |
| August | 25.9 °C | 31.3 °C | 159.77 mm |
| September | 24.1 °C | 29.4 °C | 163.07 mm |
| October | 20 °C | 25.7 °C | 134.11 mm |
| November | 14.3 °C | 20.9 °C | 119.38 mm |
| December | 9.9 °C | 17.1 °C | 112.78 mm |
| Annual | 18.3 °C | 24.1 °C | 1473.21 mm |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 10a : -1.1°C to 1.7°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |